Session: Tuesday Morning, December 3

Time: 11:25

NOAA's Pacific Marine Environmental Laboratory (PMEL) has been monitoring
U.S. Navy SOund SUrveillance System (SOSUS) data from the northeast Pacific
since 1991. Beginning in May 1995, additional hydrophone arrays were made
available to PMEL for the study of underwater earthquakes, volcanoes, and whale
acoustics. The addition of these data has made it possible for monitoring of
low-frequency (60 Hz) whale calls over large areas of the north Pacific.
Thirteen arrays in the north Pacific were grouped into five subregions:
nearshore NE Pacific, offshore NE Pacific, central Aleutians, western Aleutians,
and northwestern Pacific. SOSUS data were examined for the presence or absence
of four different call types, two each from presumed blue (Balaenoptera
musculus) and fin (B. Physalus) whales. The blue whale call types included the
A--B pair [Thompson et al., Mar. Mamm. Sci. 12, 288--292 (1996)] and the
two-part call described by Thompson and Friedl [Cetology 45, 1--19 (1982)]. Fin
whale calls were divided into two groups based on the pattern and frequency
content of the call series. Seasonal and geographic variation were found for all
four call types.